1. Field of the Invention
The present invention relates to a semiconductor device, more specifically to a semiconductor device and an assembling method for a ball grid array package.
2. Description of the Related Art
With move to higher levels of integration and improved functions of electric devices in recent years, semiconductor chips in semiconductor devices are shrinking in geometrical size, growing the degree of on-chip integration, and improving their performance. With respect to mounting technology of the semiconductor chips, a surface-mount package (SMP), such as a ball grid array (BGA), and a chip scale or chip size package (CSP) has been developed in addition to a lead-insertion package.
The surface-mount package has outer connection balls serving as electrodes arranged in an array on a bottom surface of a base substrate. A semiconductor chip provided on an upper surface of the base substrate is electrically connected to the outer connection balls. For example, a product having a semiconductor chip provided on a polyimide substrate with high heat resistance, an encapsulating resin encapsulating the semiconductor chip, and a plurality of solder balls provided on a bottom side of the polyimide substrate is widely known. In addition, a miniaturization technology of wiring boards, such as tapes and printed wiring boards, which have fine wiring patterns, has been developed to mount a miniaturized semiconductor chip thereon. A technology for a build-up wiring board having multi-lever interconnects has also been developed.
Recently, in the field of a micro-ball grid array packages, a semiconductor chip mounted on a base substrate has become extremely smaller than the base substrate. A few lines of outer connection electrodes are arranged outside of the chip mounting area. The base substrate may warp due to heat stress that occurs during the formation of the outer connection electrodes on the bottom side of the board, and it is difficult to connect solder balls to the outer connection electrodes. To maintain planarity of the base substrate, encapsulating resin, which encapsulates the semiconductor chip, is provided on the base substrate.